PET/CT findings within the contralateral tonsil following unilateral tonsillectomy.

OBJECTIVES/HYPOTHESIS In the setting of considerable variation of pharyngeal palatine tonsil fluorine 18 fluorodeoxyglucose (FDG) uptake, we mostly rely on the asymmetry between the left- and right-sided tonsils to identify underlying malignancy. The current study evaluates the FDG positron emission tomography (PET)/computed tomography (CT) findings within the contralateral tonsil among patients who had unilateral tonsillectomy and analyzes the cancer incidence in the contralateral tonsil with high FDG avidity. STUDY DESIGN A retrospective cohort study in a single high-volume tertiary cancer center. METHODS Analysis of the PET/CT scans performed at Peter MacCallum Cancer Center (Melbourne, Australia) between June 1, 2005, and December 31, 2014. RESULTS The study group consists of 160 patients who underwent 308 postunilateral tonsillectomy FDG PET/CT scans. The majority of unilateral tonsillectomies were undertaken for the treatment or diagnosis of oropharyngeal squamous cell carcinoma (85.1%).The mean follow-up time succeeding unilateral tonsillectomy was 38.2 months. Ten (6.25%) patients had relatively high contralateral tonsil FDG uptake (mean maximal standardized uptake value 6.9). Only one patient, with localized high FDG uptake but no other high uptake within the Waldeyer's ring and no previous PET/CT for comparison, underwent contralateral tonsillectomy. This was found to be benign. None of the 160 patients, including those nine patients, had developed contralateral tonsil malignancy at the end of the study period. CONCLUSION Positron emission tomography/computed tomography remains a reliable surveillance tool within the contralateral tonsil following unilateral tonsillectomy. Comparison with previous PET/CT scans and comparison with other subsites within the Waldeyer's ring, in combination with appropriate follow-up and clinical judgment, facilitate PET/CT high accuracy. LEVEL OF EVIDENCE 4. Laryngoscope, 126:2480-2483, 2016.